As the microelectronic devices are fabricated in smaller geometries there is an increasing demand for advanced materials that meet the stringent requirements of confined smaller geometries. In particular, sub-micron device geometries have become common place in the fabrication of a variety of microelectronics packages for memory and logic integrated circuits (ICs), liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) and other radio frequency (Rf) and microwave devices. For example, devices such as radio frequency integrated circuits (RFICs), micro-machine integrated circuits (MMICs), switches, couplers, phase shifters, surface acoustic wave (SAW) filters and SAW duplexers, have recently been fabricated with submicron dimensions.
With such smaller geometries comes a requirement for dielectric materials with low dielectric constants to reduce or eliminate any cross-talk between adjacent signal lines or between a signal line and a device feature (e.g. a pixel electrode) due to capacitive coupling. Although many low dielectric (low-K) materials are available for microelectronic devices, for optoelectronic devices such materials must also be broadly transparent in the visible light spectrum, not require high temperature processing (greater than 300° C.) that would be incompatible with other elements of such an optoelectronic device, and be both low-cost and feasible for large scale optoelectronic device fabrication.
Thus, it would be desirable to have a material capable of forming a self-imageable layer to avoid the need for depositing a separate imaging layer. Such material should also be easy to apply to a substrate, have a low dielectric constant (3.9 or less) and thermal stability to temperatures in excess of 250° C. Of course, it is also desirable to have such materials available at a lower cost and feature such properties as positive or negative tone photoimaging capability, aqueous base developing capability, high transparency after heat stress and low weight loss at curing temperatures. It has been reported that acrylic polymers, which are inexpensive, offer good photoimaging properties and are aqueous base developable, see for example, Japanese Patent Application Laid-open No. Hei 5-165214 and the radiation-sensitive resin composition comprising an alicyclic olefin resin disclosed in Japanese Patent Application Laid-open No. 2003-162054. Similarly, polyimides have been reported to provide good thermal stability. However, these materials have certain deficiencies and thus making them not so suitable for the applications contemplated herein. For instance, acrylics are not suitable for applications requiring high thermal stability (i.e., temperatures higher than 200° C.), and many of the polyimides in general are not suitable for either positive tone or negative tone formulations requiring aqueous base developability and generally do not exhibit desirable transparency, thus making them unsuitable in certain optoelectronic applications. Although some polyimides and polybenzoxazoles have low dielectric constants but still may not have low enough permittivity to be effective in highly integrated and/or miniaturized devices having increased wiring density and high signal speed. Furthermore, both polyimides and polybenzoxazoles require cure temperatures in excess of 300° C., thus rendering them unsuitable for many applications. One such known polyimide material is the positive tone photosensitive resin comprising a polyimide precursor and a diazoquinone-type compound disclosed in Japanese Patent No. 3,262,108.
Recently, it has been reported that certain polymers containing norbornene-type repeat units having pendent phenol groups are useful in certain microelectronic applications featuring self-image forming layer capability, when image-wise-exposed to actinic radiation, see U.S. Pat. Nos. 8,748,074 and 8,753,790, pertinent portions of which are incorporated herein. Generally, the polymers reported therein incorporate perfluoroalkyl substituted monomers in order to improve the dissolution characteristics of such compositions after image-wise exposed to suitable radiation and developed in an aqueous media. However, there are concerns in the electronic applications that presence of fluorine restricts use of such polymers containing the fluorinated monomers. For example, there is a concern of metal corrosion due to the presence of a fluoride in the dielectric polymer employed in the electronic device fabrication. In addition, the fluorinated monomers, such as for example, 2-(bicyclo[2.2.1]hept-5-en-2-ylmethyl)-1,1,1,3,3,3-hexafluoropropan-2-ol (HFANB), are expensive rendering polymers containing such monomers less attractive for such applications.
Accordingly, there is a need for cost effective permanent dielectric materials having not only self photopatternable properties but also retaining of film thickness from the unexposed regions of a positive tone formulation (i.e., low dark field loss), low thermal reflow after cure, improved stability to various chemicals and process conditions involved in the downstream process fabrication steps, such as, for example, in a device containing a redistribution layer (RDL), and/or solvent stripper operations, among others.
Thus it is an object of this invention to provide organic polymer materials having aforementioned properties for a variety of electronic and/or optoelectronic device fabrication applications.